Catalyst for recycling a plastic

ABSTRACT

A catalyst for recycling a plastic chosen from polyethylene, polypropylene, polystyrene, and combinations thereof includes a porous support having an exterior surface and at least one pore therein, a depolymerization catalyst component comprising a metallocene catalyst disposed on the exterior surface of the porous support, and a reducing catalyst component disposed in the at least one pore. The exterior surface of the porous support comprises less than 10 parts by weight of the reducing catalyst component based on 100 parts by weight of the depolymerization catalyst component as determined using Energy Dispersive X-Ray Spectroscopy (EDS). Moreover, the reducing catalyst component comprises a transition metal selected from the group of iron, nickel, palladium, platinum, and combinations thereof. The at least one pore in the porous support has an average pore size of 10 Angstroms.

RELATED APPLICATIONS

This application claims priority to and all the advantages of U.S. Provisional Patent Application Ser. No. 61/630,894, filed Dec. 21, 2011, which is expressly incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure generally relates to a catalyst for recycling a plastic. More specifically, the present disclosure relates to a catalyst for recycling the plastic that includes a depolymerization catalyst component and a reducing catalyst component.

BACKGROUND

Plastics are typically made from non-renewable petroleum resources and are often non-biodegradable. In the United States, plastics are produced in amounts exceeding 115,000 million pounds annually. Plastics are used in many industries to form products for sale in both industrial and residential markets. In industrial markets, plastics are used to form packaging, insulation, construction products, etc. In residential markets, plastics are used to form bottles, containers, and the like.

Plastics such as polyethylene terephthalate (PET), high density polyethylene (HDPE), and polyvinyl chloride (PVC), have commonly accepted Recycling Codes of from 1 to 3, respectively, as developed by the American Plastics Council. These aforementioned plastics are more widely recycled and re-used than many other types of plastics. However, plastics such as polyethylenes having Recycling Codes of 2 and 4 and some 7, polypropylene having a Recycling Code of 5, and polystyrene having a Recycling Code of 6, can also be recycled. Yet, recycling efforts for polyethylenes, polypropylene, and polystyrene have not been maximized.

Only a small fraction of the plastics produced each year are recycled and re-used. To ease in recycling, the plastics are usually crushed, melted, and/or broken down. Plastics that are not recycled and re-used present potential environmental pollution risks when discarded, are not utilized for energy or raw materials, and contribute to an increased reliance on non-renewable petroleum resources. Traditionally, plastics are recycled according to one of two methods including open- and closed-loop recycling. Closed-loop recycling involves using the plastic as an input to make the same product again. Open-loop recycling involves using the plastic as an input to make other products. For example, open-loop recycling may be used to form diesel fuel using the plastic as an input. However, neither of these methods are particularly efficient because of the complexities involved in processing plastics of different colors, textures, and consistencies and producing other products.

One particular type of open loop recycling includes decomposition of a plastic by heating, in the absence of a catalyst and oxygen, to reverse polymerize the plastic and form monomers. After the plastic is decomposed, the monomers can then be used in a variety of manufacturing or commercial processes. Traditionally, this decomposition through heating forms monomers having an inconsistent and/or unpredictable number of carbon atoms, while leaving much of the plastic unusable. Formation of monomers having unpredictable numbers of carbon atoms inhibits the monomers from being effectively recycled into other products.

Another particular type of open-loop recycling includes catalytic cracking, in the absence of oxygen, which improves on the decomposition of plastic by heating alone. As is known in the art, catalytic cracking involves reverse polymerizing a plastic, in the presence of a catalyst, to form monomers. Traditionally, the catalysts used in catalytic cracking procedures include classic Lewis acids such as AlCl₃, metal tetrachloroaluminates, zeolites, superacids, gallosilicates, metals on carbon, and basic oxides. However, many of these catalysts are ineffective in selectively cracking the plastics to form specific monomers. Although traditional catalytic cracking is more efficient in forming monomers than simple decomposition of plastics through heating alone, many of these traditional catalysts still form monomers having an inconsistent and/or unpredictable number of carbon atoms and still leave much of the plastic unusable and un-cracked.

The art, such as U.S. 2007/0083068, fails to disclose formation of a catalyst wherein a reducing catalyst component is disposed in at least one pore of a porous support and wherein an exterior surface of the porous support comprises less than 10 parts by weight of a reducing catalyst component based on 100 parts by weight of the depolymerization catalyst component as determined using Energy Dispersive X-Ray Spectroscopy (EDS). If anything, at least 50% of the reducing catalyst component would be present on the exterior surface of the porous support of this reference. Accordingly, there remains an opportunity to develop an improved method for recycling plastics.

SUMMARY OF THE DISCLOSURE AND ADVANTAGES

The present disclosure provides a catalyst for recycling a plastic chosen from polyethylene, polypropylene, polystyrene, and combinations thereof. The catalyst includes a porous support having an exterior surface and at least one pore therein, a depolymerization catalyst component comprising a metallocene catalyst disposed on the exterior surface of the porous support, and a reducing catalyst component disposed in the at least one pore. The exterior surface of the porous support comprises less than 10 parts by weight of the reducing catalyst component based on 100 parts by weight of the depolymerization catalyst component as determined using Energy Dispersive X-Ray Spectroscopy (EDS). Moreover, the reducing catalyst component comprises a transition metal selected from the group of iron, nickel, palladium, platinum, and combinations thereof. The at least one pore in the porous support has an average pore size of 10 Angstroms.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the subject disclosure will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of one embodiment of a catalyst including the porous support, the depolymerization catalyst component, and the reducing catalyst component;

FIG. 2 is a cross-sectional view of one embodiment of the catalyst;

FIG. 3 is a perspective view of another embodiment of the catalyst;

FIG. 4 is a is a perspective view of yet another embodiment of the catalyst;

FIG. 5 is a gas chromatograph illustrating the relative quantities of a narrow spectrum of hydrocarbons formed from exposure of a plastic to one embodiment of the catalyst of this disclosure;

FIG. 6 is a gas chromatograph illustrating the relative quantities of a narrow spectrum of hydrocarbons formed from exposure of a plastic to another embodiment of the catalyst of this disclosure;

FIG. 7 is a gas chromatograph illustrating the relative quantities of a spectrum of hydrocarbons formed from exposure of a plastic to catalyst of the prior art;

FIG. 8A is an EDS Spectrum of Catalyst A of the Examples—Exterior Surface;

FIG. 8B is an EDS Spectrum of Catalyst A of the Examples—Within the Pores;

FIG. 9A is an EDS Spectrum of Catalyst B of the Examples—Exterior Surface; and

FIG. 9B is an EDS Spectrum of Catalyst B of the Examples—Within the Pores.

DETAILED DESCRIPTION OF THE DISCLOSURE

The present disclosure provides a method of, and a catalyst for, recycling a plastic. The terminology “recycling” and “decomposing” may, in various non-limiting embodiments, be used interchangeably herein. The plastic of the present disclosure may be any plastic known in the art. The plastic may be a polymerization product of monomers including, but not limited to, aliphatic monomers, aromatic monomers, and combinations thereof. The plastic may be a polymerization product of monomers including unsaturated monomers such as alkenes and dienes having carbon-carbon double bonds, alkynes having carbon-carbon triple bonds, and styrene monomers. The plastic may be recyclable according to the Recycling Codes developed by the American Plastics Council. Prior to recycling, the plastic may be found in commercial products including, but not limited to, containers, packaging, insulation, construction products, and combinations thereof. However, it is contemplated that the plastic may be in any form.

In one embodiment, the plastic is selected from the group of polyethylene, polypropylene, polystyrene, and combinations thereof. Polypropylene corresponds to Recycling Code 5 and can traditionally be found in food containers, medicine bottles, etc. Polystyrene (PS) corresponds to Recycling Code 6 and can typically be found in compact disc jackets, food service applications, food trays, egg cartons, pharmaceutical containers, cups, plates, cutlery, and the like.

In another embodiment, the polyethylene is selected from the group of low density polyethylene (LDPE), which corresponds to Recycling Code 4, linear low density polyethylene (LLDPE), which may be classified under Recycling Code 7, high density polyethylene (HDPE), which corresponds to Recycling Code 2, and combinations thereof. Low density polyethylene may be found in dry cleaning products, in food storage bags and bottles, and the like. Linear low density polyethylene is typically found in liquid containers, food containers, etc. High density polyethylene is traditionally found in food, cosmetic, and detergent bottles, in storage containers, in cereal box liners, in grocery, trash and retail bags, etc. It is contemplated that the plastic may be atactic, isotactic, hemi-isotactic, or syndiotactic, as is known in the art. For descriptive purposes only, the chemical structures of polyethylene, polypropylene, and polystyrene are shown below:

wherein n may be any integer.

-   Also for descriptive purposes only, generic chemical structures of     atactic, isotactic, and syndiotactic polypropylene are shown below:

wherein n may be any integer.

Before the plastic is decomposed, the method may include the steps of processing the plastic with physical and/or chemical treatments and introducing the plastic into a vessel. These steps are independent of each other and do not necessarily have to be performed in the method. It is contemplated that the steps of processing the plastic and introducing the plastic into the vessel, if included in the method, may occur in any order.

Typically, the plastic is processed with the physical and/or chemical treatments to ease introduction into the vessel. When processed with physical treatments, the plastic is typically cleaned to remove dirt, oil, grease, detergents, food, and exogenous plant and animal contaminants. The plastic may be cleaned with any method known in the art. Typically, the plastic is cleaned using pressurized water jets, floatation, surfactants, scrubbers and the like, and combinations thereof. The plastic may also be reduced in size through any method known in the art including, but not limited to, shredding, grinding, heating, melting, burning, smashing, dissolving, tearing, crushing, and combinations thereof. The plastic may be reduced to any size including, but not limited to, powder. The plastic may also be physically treated through stirring, mixing, sonicating, through use of radiowaves, magnetic energy, and light energy, and combinations thereof. The plastic may also be treated with the chemical treatments including combination with catalysts, enzymes, fillers, acids, bases, salts, cationic and anionic compounds, processing agents, and combinations thereof. Most typically, the plastic is cleaned, shredded, and melted into a molten state.

It is to be understood that melting the plastic into a molten state may or may not decompose the plastic depending on temperature and rate of heating. The plastic may be heated at any rate and to any temperature. In one embodiment, the plastic is heated to a temperature of from 75° C. to 250° C., more typically of from 100° C. to 200° C., and most typically of from 150° C. to 200° C., to melt the plastic. In yet another embodiment, the plastic is heated to a temperature of 150° C. to melt the plastic. In another embodiment, the plastic is typically heated at a rate of from 10 to 1000, more typically of from 50 to 500, and most typically of from 100 to 200,° C./second, to melt the plastic. It is contemplated that the plastic may be melted in one or more heated vessels.

Referring now to the optional step of introducing the plastic into the vessel, the plastic may be introduced into the vessel in any setting and in any amount. The plastic may be introduced into the vessel in laboratories on a gram and smaller scale and in industrial recycling facilities on a kilogram to kiloton and larger scale. The vessel may be any vessel known in the art and may include one or more laboratory and/or industrial size vessels. In one embodiment, the plastic is continuously fed into the vessel for decomposition, thereby making the method of the instant disclosure continuous. It is also contemplated that the method may be performed batch-wise, i.e., discontinuously. All of these may take place in the absence of oxygen.

The vessel may be a reactor. The reactor may be any reactor known in the art including, but not limited to, continuous screw reactors, plug reactors, and combinations thereof. In one embodiment, the reactor includes both a continuous screw reactor and a plug reactor. The reactor may also be operated in any type of mode including, but not limited to, batch and continuous modes, as first introduced above. Typically, the reactor is operated in continuous mode to reduce energy consumption, operating costs, size of the reactor, running time, and down time. The reactor may further be operated at any temperature. In one embodiment, the reactor is heated discontinuously from room temperature to a desired temperature for every cycle of the method. In another embodiment, the reactor is heated to the desired temperature and continuously maintained at the desired temperature. Typically, the reactor is heated to a temperature of from 100° C. to 600° C., more typically of from 400° C. to 600° C., and most typically of from 350° C. to 450° C.

Referring now to the step of decomposing the plastic, the plastic is typically decomposed in the vessel. The plastic may be decomposed by any method known in the art including, but not limited to, heating, actinic and microwave radiation, and combinations thereof. It is contemplated that the temperature of decomposition may be the same as the aforementioned temperatures for melting the plastic or may be different. Typically, the plastic is decomposed at a temperature of from 100° C. to 600° C., more typically of from 400° C. to 600° C., and most typically of from 350° C. to 450° C.

In one embodiment, the step of decomposing the plastic includes the step of pyrolyzing the plastic. As is known in the art, pyrolysis includes rapid heating of the plastic, i.e., heating the plastic at a rate of at least 50° C./sec, to at least partially reverse polymerize the plastic and form the hydrocarbons. In another embodiment, the step of decomposing the plastic includes the step of thermolyzing the plastic. As is also known in the art, thermolysis includes gradual heating of the plastic, i.e., heating the plastic at a rate of at least 1° C./sec, to at least partially reverse polymerize the plastic and form the hydrocarbons.

In one embodiment, the method includes the step of introducing a catalyst 10 into the vessel as. Typically, the catalyst 10 is introduced into the vessel after the plastic is introduced into the vessel and as the plastic is decomposing. The catalyst 10 may be introduced into the vessel in a solid, liquid, or gaseous state, or in a combination of states. The plastic may be decomposed in the presence of from 0.1 part of the catalyst per one million parts of the plastic to 100 parts of the catalyst per 100 parts of the plastic. Alternatively, the plastic may be decomposed in the presence of from 1 part of the catalyst per one million parts to 100 parts of the catalyst per 100 parts of the plastic, from 10 parts of the catalyst per one million parts to 100 parts of the catalyst per 100 parts of the plastic, from 100 part of the catalyst per one million parts to 100 parts of the catalyst per 100 parts of the plastic, or from 1000 parts of the catalyst per one million parts to 100 parts of the catalyst per 100 parts of the plastic. Alternatively, the plastic may be decomposed in the presence of from 0.01 to 100, 0.1 to 100, 1 to 100, 10 to 90, 20 to 80, 30 to 70, or 40 to 60 parts of the catalyst per 100 parts of the plastic.

The method includes decomposing the plastic in the presence of the catalyst 10 to form hydrocarbons. The catalyst 10 includes a porous support 12, a depolymerization catalyst component A, and a reducing catalyst component B, as shown in FIGS. 1-4. The plastic is typically decomposed in the presence of the catalyst 10 to form one or more hydrocarbons. The one or more hydrocarbons typically each independently have 4 to 40, 5 to 39, 6 to 38, 7 to 37, 8 to 36, 9 to 35, 10 to 34, 11 to 33, 12 to 32, 13 to 31, 14 to 30, 15 to 29, 16 to 28, 17 to 27, 18 to 26, 19 to 25, 20 to 24, 21 to 23, or 22 to 23, carbon atoms (carbons), or any combination thereof In one embodiment, the hydrocarbons each have from 4 to 40 carbons. In other embodiments, the hydrocarbons have from 5 to 25 carbons. In some embodiments, the hydrocarbons have from 11 to 25 carbons. It is to be appreciated the terminology set forth above describe a number of carbon atoms typically describes a molecular distribution of the hydrocarbons formed or the total number of carbon atoms in each of the one or more hydrocarbons. In various embodiments, the plastic is depolymerized in the presence of the depolymerization catalyst component A to form hydrocarbons, e.g. having 5 to 25 carbons. More specifically, in certain embodiments, the plastic is depolymerized in the presence of the depolymerization catalyst component A to form a mixture of saturated and unsaturated hydrocarbons having, e.g. 5 to 25 carbons.

In other embodiments, the unsaturated hydrocarbons having, e.g. 5 to 25 carbons, are reduced in the presence of the reducing catalyst component B to form saturated hydrocarbons having 5 to 25 hydrocarbons. Without reducing the unsaturated hydrocarbons in the presence of the reducing catalyst component B, the unsaturated hydrocarbons may undesirably continue to depolymerize in the presence of the depolymerization catalyst component A. Typically, hydrocarbons having 5 to 25 carbons are suitable for use as/in diesel fuel. In contrast, hydrocarbons having 5 to 10 carbons are typically suitable for use as/in gasoline. Typically, the depolymerization catalyst component A and the reducing catalyst component B cooperate to decompose the plastic. In various embodiments, if gasoline fuel is a desired output or result, the molecular distribution for the hydrocarbons formed may be from 4 to 16, from 5 to 11, or from 5 to 10 carbons. In other embodiments, if diesel fuel is a desired output or result, the molecular distribution for the hydrocarbons formed may be from 5 to 35, from 10 to 30, or from 11 to 24 carbons. In one embodiment, the diesel fuel is further defined as light diesel fuel and has a cetane value of from 42 to 55.

Referring back to the porous support 12, the porous support has an exterior surface 14 and defines at least one pore 16 therein, as shown in FIGS. 1-4. The porous support 12 may have or be any structure known in the art including a crystalline or an irregular structure. In addition, the at least one pore 16 may be defined uniformly or randomly throughout the porous support 12. In various embodiments, the porous support 12 includes two or a plurality of pores 16 wherein each pore 16 independently has a uniform or irregular structure. Any one pore may have a structure that is the same or different from the structure of any other pore. The at least one pore 16 typically extends into the porous support 12, and may extend through the porous support 12, or a combination thereof. Typically, the porous support 12 has a crystalline structure wherein the plurality of pores 16 may be defined and/or disposed uniformly or heterogeneously or randomly through or on or in the porous support 12. The porous support 12 may be further defined as a molecular sieve, clay, glass, ceramic, charcoal, silica gel, or sol-gel. In various embodiments, the porous support 12 is further defined as a molecular sieve.

Typically, the at least one pore 16 has a pore size of from 3 to 20, from 3 to 12, from 3 to 6 angstroms (Å). Alternatively, the at least one pore 16 has a pore size of from 3 to 19, from 4 to 18, from 5 to 17, from 6 to 16, from 7 to 15, from 8 to 14, from 8 to 13, from 9 to 12, from 9 to 11 Å. The pore size may be alternatively described as any value, or range of values, both whole and fractional, within or between any one or more values described above. In various embodiments, the aforementioned pore size may vary by ±1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, etc. %. Without intending to be bound by any particular theory, it is believed that the pore size contributes to the decomposition of the hydrocarbons because the at least one pore 16 permits hydrocarbons of particular molecular weight and/or sizes into the at least one pore 16 thereby preventing or minimizing further depolymerization, as described in detail below. A non-limiting example of a suitable molecular sieve is a 13X molecular sieve. The 13X molecular sieve has a pore size of about 10 Å.

In other embodiments, the molecular sieve is further defined as a zeolite. Zeolites are hydrated silicates of aluminum and may include sodium and/or calcium. One common chemical formula of zeolites is Na₂.Al₂O₃.xSiO₂.xH₂O. Suitable non-limiting examples of zeolites include AFG, IFR, OFF, ABW, ACO, SAO, ASV, ISV, OSO, AET, AEI, SAS, BEA, ITE, PAR, AFI, AEL, SAT, BIK, JBW, PAU, AFX, AEN, SAV, BOG, KFI, RON, ANA, AFN, SBE, BRE, LIO, RSN, AST, AFO, SBS, CAS, LOV, RTE, BPH, AFR, SBT, CFI, LTN, RTH, CAN, AFS, VFI, CHI, MAZ, RUT, CGS, AFT, WEI, CON, MEI, SFE, CHA, AFY, ZON, DAC, MEL, SFF, DFT, AHT, DDR, MEP, SGT, EDI, APC, DOH, MFI, STF, ERI, APD, DON, MFS, STI, FAU, ATN, EAB, MON, STT, GIS, ATO, EMT, MOR, TER, LAU, ATS, EPI, MSO, TON, LEV, ATT, ESV, MTF, TSC, LOS, ATV, EUO, MTN, VET, LTA, AWO, FER, MTT, VNI, LTL, AWW, FRA, MTW, VSV, MER, CGF, GME, MWW, WEN, PHI, CLO, GON, NAT, YUG, RHO, CZP, GOO, NES, SOD, DFO, HEU, NON, THO, OSI, ZSM, and combinations thereof. A non-limiting example of a suitable zeolite is a ZSM 34 zeolite. The ZSM 34 zeolite has a pore size of about 5 Å.

Referring back, the depolymerization catalyst component A is disposed on the exterior surface 14 of the porous support 12 for depolymerizing the plastic to form the hydrocarbons. More specifically, the depolymerization catalyst component A may be disposed on and in direct contact with, or on and spaced apart from, the exterior surface 14 of the porous support 12. In certain embodiments, the depolymerization catalyst component A may be disposed on and in direct contact with, or on and spaced apart from, the exterior surface 14 and the depolymerization catalyst component A may be disposed in and in direct contact with, or in and spaced apart from, an interior of the at least one pore 16 of the porous support 12. Said differently, the depolymerization catalyst component A may be disposed both on the exterior surface 14 of the porous support and simultaneously in the at least one pore 16 of the porous support 12.

The depolymerization catalyst component A includes or is a Ziegler-Natta catalyst, a Group IIA oxide catalyst, or a combination thereof. As described above, the plastic is typically depolymerized in the presence of the depolymerization catalyst component A to form the hydrocarbons. In some embodiments, the depolymerization catalyst component A is further defined as a Ziegler-Natta catalyst. For example, the Ziegler-Natta catalyst may be or include one or more heterogeneous supported catalysts such as TiCl₃ supported on MgCl₂ and homogenous catalysts such as metallocene catalysts and non-metallocene catalysts. Typically, a metallocene catalyst is or includes a metal atom such as Ti, Zr, or Hf complexed with two organic ligands. Typically, a non-metallocene catalyst includes various metal atoms complexed with a variety of ligands with the ligands including oxygen, nitrogen, phosphorus, and/or sulfur.

In various other embodiments, the Ziegler-Natta catalyst is further defined as a metallocene catalyst. Although the exact mechanism of depolymerizing the plastic in the presence of the metallocene catalyst is not known, the mechanism is likely influenced by kinetic, thermodynamic, electronic, and/or steric interactions of the plastic and the metallocene catalyst and may utilize a type of reverse-Arlman-Cossee mechanism to depolymerize the plastic. Without intending to be limited by any particular theory, it is believed that the mechanism involves coordination of carbon atoms in the plastic with the metal atom of the metallocene catalyst involving pi bonding- and anti-bonding-orbitals of the carbon atoms and d-orbitals of the metal atom.

The metallocene catalyst may be chiral or achiral, may be symmetric or asymmetric, and may be homogeneous or heterogeneous. The metallocene catalyst may include any organic or inorganic moieties known in the art. The terminology “metallocene catalyst” includes both metallocene and post-metallocene catalysts. As is known in the art, metallocenes are organometallic coordination compounds that include cyclopentadienyl derivatives of a transition metal or metal halide, i.e., a constrained metal site is sterically hindered due to orientation between two pi-carbocyclic ligands. Three non-limiting examples of suitable metallocenes include dicyclopentadienyl-metals having the general formula (C₅H₅)₂M, dicyclopentadienyl-metal halides having the general formula (C₅H₅)₂MX₁₋₃, and monocylopentadienyl-metal compounds with the general formula (C₅H₅)₂MR₁₋₃, wherein X is a halogen and R is an organic moiety. When the two pi-carbocyclic ligands are unbridged, the metallocene is non-stereorigid and typically has C₂v symmetry, i.e., the metallocene has a plane of symmetry. When the two pi-carbocyclic ligands are bridged, a stereorigid metallocene, also known as an ansa metallocene, is formed and typically has C₁, C₂, or C_(s) symmetry, wherein a C_(s) symmetric molecule has a plane of symmetry and is not chiral. In one embodiment, the plastic is atactic and the metallocene catalyst is an achiral C₂v symmetric metallocene. In another embodiment, the plastic is hemi-isotactic and the metallocene catalyst is a C₁ symmetric metallocene. In yet another embodiment, the plastic is isotactic and the metallocene catalyst is a chiral C₂ symmetric metallocene. In a further embodiment, the plastic is syndiotactic and the metallocene catalyst is a C_(s) symmetric metallocene.

In other embodiments, the metallocene catalyst is selected from the group of Kaminsky catalysts, Brintzinger catalysts, Ewen/Razavi catalysts, and combinations thereof In these other embodiments, the metallocene catalyst is or includes a Kaminsky catalyst.

As is known in the art, Kaminsky and Brintzinger catalysts are based on metallocenes of Group IV transition metals and include halogens. These metallocene catalysts are typically homogeneous. For descriptive purposes only, generic chemical structures of Kaminsky and Brintzinger catalysts are shown below:

wherein M is typically a Group IV transition metal including, but not limited to, titanium, zirconium, hafnium, and X is typically a halogen.

In certain embodiments, the metallocene catalyst includes zirconium. In various embodiments, the metallocene catalyst including zirconium is further defined as bis(cyclopentadienyl)zirconium(IV). In other embodiments, the metallocene catalyst is or includes dichlorobis(2-methylindenyl)zirconium (IV). In yet other embodiments, the metallocene catalyst is dichlorobis(2-methylindenyl)zirconium (IV), which has a chemical formula of C₂₀H₁₈Cl₂Zr, a molecular weight of 420.49 grams/mole, and a CAS number of 165688-64-2, and is commercially available from Sigma Aldrich Corporation of St. Louis, Mo. For descriptive purposes only, a chemical structure of dichlorobis(2-methylindenyl)zirconium (IV) is shown below:

As is also known in the art, Ewen/Razavi catalysts are similar to Kaminsky and Brintzinger catalysts. These catalysts are also typically homogeneous. For descriptive purposes only, a common chemical structure of a Ewen/Razavi catalyst are shown below:

wherein M is typically a Group IV transition metal, E is typically selected from the group of carbon and silicon, and R′ and R″ may each independently include any organic moiety and may be the same or may be different.

The post-metallocene catalysts are typically homogeneous single-site systems, such that catalytic properties can be controlled by modification of the structure of the post-metallocene catalyst. Many post-metallocene catalysts include early transition metals. However, late transition metals may also be included such as nickel, palladium, iron, or combinations thereof. Non-limiting examples of post-metallocene catalysts that are suitable for use as the depolymerization catalyst component A are Brookhart, Grubbs, and Fujita catalysts. For descriptive purposes only, common chemical structures of the Brookhart, Grubbs, and Fujita catalysts are shown below:

wherein R may be any organic or inorganic moiety known in the art.

For descriptive purposes only, the depolymerization of polyethylene, polypropylene, and polystyrene, in the presence of the metallocene catalyst and heat, is shown below in three separate reaction schemes:

wherein n may be any integer and typically is from 1 to 40.

In other embodiments, the depolymerization catalyst component A is or includes a Group IIA oxide catalyst. The Group IIA oxide catalyst may be or include one or more oxides of beryllium, magnesium, calcium, strontium, barium, radium, or combinations thereof. In certain embodiments, the Group IIA oxide catalyst is further defined as magnesium oxide, calcium oxide, barium oxide, and/or combinations thereof. Typically, the Group IIA oxide is further defined as barium oxide.

In various embodiments, the depolymerization catalyst component A includes molecules with customizable alkaline and acidic sites. If the depolymerization catalyst component A includes alkaline and acidic sites in the same molecule, the alkaline and acidic sites may be in the form of aluminum titanates, mixture of aluminum hydroxides or oxides, titanium oxides, titania, alkali or alkaline metal titanate, or combinations thereof. Specifically, the depolymerization catalyst component A may include the aluminum and titanium oxides with varying ratios of acidity and alkalinity.

Referring back, the reducing catalyst component B is disposed in the at least one pore 16 for reducing the hydrocarbons. More specifically, the reducing catalyst component B may be disposed in and in direct contact with, or in and spaced apart from, an interior of the at least one pore 16 of the porous support 12. The reducing catalyst component B may be any reducing catalyst known in the art. As described above, the hydrocarbons are typically reduced in the presence of the reducing catalyst component B in the at least one pore 16 of the porous support 12. It is believed that the hydrocarbons which can enter the at least one pore 16 of the porous support 12 are reduced. Once the hydrocarbons enter the at least one pore 16, the hydrocarbons may be reduced which may result in the termination of the depolymerization of the hydrocarbons within the at least one pore 16. By controlling the pore size of the at least one pore 16, the molecular distribution of the hydrocarbons may be controlled. For example, the catalyst 10 for decomposing the plastic having a pore size of 10 Å may form hydrocarbons having 5 to 25 carbon which are suitable for use as diesel fuel while the catalyst 10 for decomposing the plastic having a pore size of 5 Å may form hydrocarbons having a lower molecular distribution which are suitable for use as gasoline fuel.

The reducing catalyst component B may be or include mono- and/or di-hydride catalysts, and/or metallic catalysts including, but not limited to, platinum, palladium, nickel, rhodium, ruthenium, iridium, titanium, and combinations thereof. In certain embodiments, the reducing catalyst component B is or includes a transition metal catalyst. The transition metal catalyst may be or include a transition metal selected from the group of iron, nickel, palladium, platinum, and combinations thereof.

In various embodiments, the reducing catalyst component B is or includes a Group IA hydride catalyst, a Group IIA hydride catalyst, or a combination thereof. The Group IA hydride catalyst may be or include lithium aluminum hydride (LAH), sodium hydride, or a combination thereof. The Group IIA hydride catalyst may be or include magnesium hydride, calcium hydride, or a combination thereof.

In other embodiments, the reducing catalyst component B is selected from the group of Wilkinson's catalyst, Crabtree's catalyst, and combinations thereof. For descriptive purposes only, the chemical structures of Wilkinson's and Crabtree's catalysts are shown below:

For descriptive purposes only, the reaction of the reducing catalyst component B with the hydrocarbons is shown below in three separate reaction schemes:

wherein n may be any integer.

In certain embodiments, the exterior surface 14 is substantially free of the reducing catalyst component B and/or the at least one pore 16 is substantially free of the depolymerization catalyst component A. The terminology “substantially free of the reducing catalyst” describes an amount of the reducing catalyst component B on the exterior surface 14 of less than 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 part(s) by weight based on 100 parts by weight of the depolymerization catalyst component A on the exterior surface 14, as determined using Energy Dispersive X-Ray Spectroscopy (EDS). The terminology “substantially free of the depolymerization catalyst” describes an amount of the depolymerization catalyst component A in the at least one pore 16 of less than 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 part(s) by weight based on 100 parts by weight of the reducing catalyst component B in the at least one pore 16, as determined using Energy Dispersive X-Ray Spectroscopy (EDS). In other embodiments, the reducing catalyst component B is different from the depolymerization catalyst component A.

In various embodiments, the catalyst 10 consists essentially of or consists of the porous support having an exterior surface and at least one pore therein; the depolymerization catalyst component that is bis(cyclopentadienyl)zirconium(IV) and is disposed on the exterior surface of the porous support; and the reducing catalyst component disposed in the at least one pore; wherein the exterior surface of the porous support comprises less than 10 parts by weight of the reducing catalyst component based on 100 parts by weight of the depolymerization catalyst component as determined using Energy Dispersive X-Ray Spectroscopy (EDS), wherein the reducing catalyst component comprises a transition metal selected from the group of iron, nickel, palladium, platinum, and combinations thereof, and wherein the at least one pore in the porous support has an average pore size of 10 Angstroms. The terminology “consists essentially of” may describe an embodiment that is free of other depolymerization catalysts, other reducing catalysts, other metals, etc.

The catalyst 10 for decomposing the plastic may also include, and/or be utilized with, a reducing agent. The reducing agent may react with the hydrocarbons and acts in concert with the reducing catalyst component B to reduce any hydrocarbons having carbon-carbon double and triple bonds to hydrocarbons having carbon-carbon single bonds, i.e., saturated monomers or hydrocarbons. The reducing agent may be any reducing agent known in the art and typically includes hydrogen gas (H₂), metal hydrides catalyzed by transition metals, and combinations thereof. Typically, the reducing agent includes H₂ modified with nitrogen gas (N₂) added as a gas stream to aid in eventual removal of the monomers. The reducing agent may react in a symmetrical or asymmetrical manner and in a directed or non-directed manner.

The catalyst 10 for decomposing the plastic may also include and/or be utilized with one or a plurality of co-catalysts. The co-catalyst is typically utilized to increase catalyst functionality and efficiency. If the co-catalyst is included, the co-catalyst is selected from the group of methyl aluminoxane, alumoxane, alkylaluminums such as trimethylaluminum and triethylaluminum, and halo-alkyls such as di ethyl aluminum chloride, di ethyl aluminum bromide, di ethyl aluminum iodide, and combinations thereof. Additionally, if the co-catalyst is included, the co-catalyst may be present in any amount. In various embodiments, the co-catalyst is present in an amount of less than or equal to 100, less than or equal to 50, or less than or equal to 10, parts by weight based on 100 parts by weight of the depolymerization catalyst component A.

The catalyst 10 for decomposing the plastic may further include and/or be utilize one or more of a plurality of modifiers. It is contemplated that the modifier may be added to the depolymerization catalyst and/or the co-catalyst. Although any modifier known in the art may be used, typically, the modifier is selected from the group of carboxylic acid esters, amines, cycloalkyltrienes, fluoride ions, ethers, ketones, phosphines, organophosphates, and combinations thereof. The modifier is typically added to the catalyst 10 and/or co-catalyst to increase catalyst functionality and efficiency. If the modifier is included, the modifier is typically present in an amount of less than or equal to 100, more typically of less than or equal to 50, and most typically of less than or equal to 10, parts by weight per 100 parts by weight of the depolymerization catalyst component A.

In various embodiments, the reducing catalyst component is deposited on the inner surface of the pores (i.e., in the pores) and the depolymerization catalyst component is deposited on the outer surface of the porous support. In theory, only the oligomers which could enter the pores of the porous support will undergo hydrogenation. The oligomers outside the porous support will undergo catalytic thermal depolymerization generating smaller and smaller oligomers. Once the oligomers enter the pores, the oligomers will be reduced which results in the termination of the depolymerization of the oligomers within the pores. By controlling the pore sizes, one will be able to control the molecular distribution of the oligomers.

In other embodiments, the method for depositing the catalysts on either the inner surface of the pores, i.e., in the pores, or the outer surface of the porous support is described below. If the catalyst is to be present on both the inner surface and the outer surface, the catalyst is dissolved in a suitable solvent at a concentration desired and added to the porous support. Evaporation of the solvent and then heating at a temperature higher than the boiling point of the solvent for an extended period of time will ensure evaporation of all the solvents, leaving behind the catalyst, finely deposited, on the inner surface of the pores and outer surface of the porous support.

To deposit the catalyst only on the outer surface of the porous support, the porous support is soaked in enough water to fill the pores of the porous support completely. Next, the outer surface is air-dried, e.g. for ten minutes. The porous support is then soaked in a water-immiscible solvent containing the catalyst. The water-immiscible solvent is filtered and the solvent is removed gently, leaving the catalyst deposited on the outside of the porous support. The water is then evaporated from the pores of the porous support by raising the temperature, e.g. to 110° C.

To deposit the catalyst only on the inner surface of the pores of the porous support, the porous support is soaked in a solvent containing the catalyst dissolved within. The solvent is then removed using heat and a flow of air, leaving the catalyst deposited on the inner surface of the pores and the outer surface of the porous support. Next, the porous support is soaked in water or a denser solvent to fill in the pores of the porous support. After gentle drying of the outer surface, while leaving the pores filled with water or the denser solvent, the outer surface is exposed to a solvent to dissolve away the catalyst on the outer surface. Afterwards, the water or the denser solvent is removed from the pores by exposing the porous support to a stream of air at higher temperature.

As just one example, 100 g of ZSM 34 zeolite (or also commonly known as a porous support), is soaked in 20 mL of a 10% solution of H₂PtCl₄ in water for 30 minutes and then dried using a flow of nitrogen and then at 100° C. for 2 hours. The porous support is then soaked in nitrobenzene (density 1.196) for 30 minutes, filtered and the solvent on the outer surface removed using a stream of nitrogen. The porous support is then soaked in water with gentle agitation or 2 hours to dissolve away any H₂PtCl₄ on the surface. The porous support is then filtered again and the outer surface dried with a stream of nitrogen. The porous support is then soaked in a 20 mL of 10% solution of AlCl₃ in Toluene for 30 minutes. The solvent is removed under a stream of nitrogen and then the outer surface is dried. To this, a 1 M solution of sodium hydroxide was added, to convert the aluminum chloride into hydroxide. The porous support is then filtered, dried with a stream of nitrogen, then dried at 100° C., followed by drying at 210° C. to remove the nitrobenzene from inside the pores. Then the porous support is placed in a furnace at 600° C. for 5 hours until the Al(OH)₃ on the outer surface is converted to Al₂O₃ and the H₂PtCl₄ inside the pores is converted to finely divided Pt. Similar schemes can be used to deposit other catalysts (for example TiO2, metallocenes, SiO2, ZnO) on the outer surface of the porous support and deposit Pt or Pd or Ni in the inner surface of the pores.

The method may also include the step of introducing the reducing agent, different from the reducing catalyst component, into the vessel and/or reducing the hydrocarbons in the presence of the reducing agent. The reducing agent is typically selected from the group of hydrogen gas (H₂), metal hydrides catalyzed by transition metals, and combinations thereof, but may be any known in the art. In one embodiment, the reducing agent includes H₂. In another embodiment, the reducing agent includes H₂ modified with nitrogen gas (N₂) added as a gas stream to the vessel to aid in eventual removal of the hydrocarbons from the vessel. The reducing agent may react with the plastic alone, with the hydrocarbons, with the catalyst 10, with the depolymerization catalyst component A and/or with the reducing catalyst component B. The reducing agent may react in a symmetrical or asymmetrical manner and in a directed or non-directed manner. The reducing agent may be added to the vessel in any amount and at any pressure. The reducing agent typically reacts with the hydrocarbons and acts in concert with the catalyst 10 to at least partially reduce hydrocarbons having carbon-carbon double and triple bonds to hydrocarbons having carbon-carbon single bonds, i.e., saturated hydrocarbons. The reducing agent may be added at any point in the method. Typically, the reducing agent is added to the vessel after the plastic has been added to the vessel and the plastic is decomposed to at least partially form the hydrocarbons. In one embodiment, the catalyst 10 and the reducing agent are present together in the vessel and act synergistically to depolymerize the plastic and reduce the hydrocarbons simultaneously. Typically, the reducing agent is added in an amount of from 0.5 to 5, more typically of from 0.6 to 2, and most typically of from 0.7 to 1, moles, per one mole of the plastic. Typically, the reducing agent is added at a pressure of from 1 to 20, more typically of from 1 to 10, and most typically of from 1 to 2, atmospheres.

In certain embodiments, the plastic is decomposed in the presence of from 0.1 part of the catalyst per one million parts of the plastic to 100 parts of the catalyst per 100 parts of the plastic, wherein the depolymerization catalyst is bis(cyclopentadienyl)zirconium(IV), wherein the reducing catalyst is palladium, wherein the porous support is further defined as 13X molecular sieve, and wherein the method further includes the step of reducing the hydrocarbons in the presence of hydrogen gas.

In addition to the aforementioned steps, the method may also include the step of monitoring the formation of the hydrocarbons. The hydrocarbons may be monitored online, offline, or through a combination of both online and offline monitoring. Also, the step of monitoring may include utilizing any monitoring technique known in the art. The monitoring technique may include, but is not limited to, spectroscopy, and chromatography. The spectroscopy may include mass, infrared, atomic emission, atomic absorption, nuclear magnetic resonance, Ramen, fluorescence, x-ray, atomic fluorescence, plasma emission, direct-current plasma, inductively-coupled plasma, laser induced breakdown, laser-induced plasma, microwave-induced plasma, spark and/or arc, UV, photoemission, force, dielectric, circular dichroism, rotational, vibrational, rigid rotor, EPR, spectral power distribution, metamerism, spectral reflectance, acoustic, dynamic mechanical, electron energy loss, and Auger electron, spectroscopies, and combinations thereof. The chromatography may include gas, liquid, ion-exchange, affinity, thin layer, supercritical fluid, and column, chromatographies, and combinations thereof. In one embodiment, the step of monitoring includes a combination of gas chromatography and mass spectroscopy.

It is also contemplated that the method may include the step of purifying the hydrocarbons. The hydrocarbons may be purified by any method known in the art. In one embodiment, the hydrocarbons are distilled to increase purity and separate the hydrocarbons from any residue of the decomposed plastic. In another embodiment, the hydrocarbons having from 4 to 40 carbon atoms are distilled to separate fractions of hydrocarbons having from 4 to 14 carbon atoms and/or fractions of hydrocarbons having from 11 to 25 carbon atoms. It is contemplated that the hydrocarbons having from 4 to 14 carbon atoms and/or the hydrocarbons having from 11 to 25 carbon atoms may include gasoline, diesel fuel, or a combination thereof that can be directly sold at commercial gas stations and used in automobiles.

The method may further include the step of adding an octane increasing agent to the plastic and/or hydrocarbons. The octane increasing agent may be any octane increasing agent known in the art including, but not limited to, aromatic hydrocarbons. Typically, the octane increasing agent includes ethylbenzene from reduction of styrene from polystyrene. In one embodiment, there is sufficient ethyl benzene formed from the decomposition of the instant plastic such that the octane increasing agent does not need to be added to the hydrocarbons. In another embodiment, the octane increasing agent is typically added in an amount of less than or equal to 30, more typically of less than or equal to 20, and most typically of less than or equal to 10, parts by weight per 100 parts by weight of the plastic. It is to be understood that if the plastic includes polystyrene, the octane increasing agent may not need to be added or may be added in lesser amounts. After decomposition of the plastic, the hydrocarbons may be removed by boiling or with a stream of gas including, but not limited to, helium, neon, argon, krypton, xenon, nitrogen, hydrogen, and combinations thereof.

EXAMPLES Inventive Example 1

A 0.4% solution of PdCl₂ is prepared by the dilution of 0.4 g of PdCl₂ in 100 g of solvent wherein the solvent includes water acidified with HCl such that the solvent is visibly clear. 50 ml of the 0.4% solution of PdCl₂ is combined with a 13X molecular sieve which includes an exterior surface and at least one pore. The 13X molecular sieve is present in an amount such that total pore volume of the 13X molecular sieve (as provided by the commercial supplier) is more than 50 ml. This typically ensures that the 50 ml 0.4% solution of PdCl₂ impregnates the at least one pore through capillary action. The 13X molecular sieve combined with PdCl₂is then dried for 24 hours at a temperature of 110° C. 0.5 g of sodium borohydride is then combined with 60 ml of water to form a sodium borohydride solution. The sodium borohydride solution is then combined with the dried 13X molecular sieve to reduce the PdCl₂ to Pd and then dispose the Pd in the at least one pore wherein the Pd is the reducing catalyst component thereby forming a 13X molecular sieve including the Pd. The 13X molecular sieve including Pd is then dried for 24 hours at a temperature of 110° C.

The at least one pore of the 13X molecular sieve including the Pd is then impregnated with 50 ml of water. 0.2 g of bis(cyclopentadienyl)zirconium(IV) (Zr) is combined with 150 ml of toluene to form a mixture. The mixture and the 13X molecular sieve including the Pd are combined, air dried for 12 hours, and then dried for 48 hours at 110° C. to dispose Zr, as the depolymerization catalyst component A, on the exterior surface thereby forming a 13X molecular sieve including the Zr disposed on the exterior surface and the Pd disposed in the at least on pore.

Inventive Example 2

A 0.4% solution of PdCl₂ is prepared by the dilution of 0.4 g of PdCl₂ in 100 g of solvent wherein the solvent includes water acidified with HCl such that the solvent is visibly clear. 50 ml of the 0.4% solution of PdCl₂ is combined with a 13X molecular sieve which includes an exterior surface and at least one pore. The 13X molecular sieve is present in an amount such that total pore volume of the 13X molecular sieve is more than 50 ml. This typically ensures that the 50 ml 0.4% solution of PdCl₂ impregnates the at least one pore through capillary action. The 13X molecular sieve combined with PdCl₂ is then dried for 24 hours at a temperature of 110° C. 0.5 g of sodium borohydride is then combined with 60 ml of water to form a sodium borohydride solution. The sodium borohydride solution is then combined with the dried 13X molecular sieve to reduce the PdCl₂ to Pd and then dispose the Pd in the at least one pore wherein the Pd is the reducing catalyst component thereby forming a 13X molecular sieve including the Pd. The 13X molecular sieve including Pd is then dried for 24 hours at a temperature of 110° C.

0.2 g of bis(cyclopentadienyl)zirconium(IV) (Zr) is combined with 100 ml of toluene and 150 ml of methyl ethyl ketone to form a mixture. The mixture and the 13X molecular sieve including the Pd are combined, air dried for 12 hours, and then dried for 24 hours at 110° C. to dispose Zr, as the depolymerization catalyst component on the exterior surface and in the at least one pore thereby forming a 13X molecular sieve including the Zr disposed on the exterior surface and in the at least one pore, and the Pd disposed in the at least one pore.

Comparative Example 1

The catalyst of Comparative Example 1 includes the same porous support as above but does not include the depolymerization catalyst component disposed on the exterior surface and the reducing catalyst component disposed in the at least one pore. Instead, bis(cyclopentadienyl)zirconium(IV), as the depolymerization catalyst component, is disposed on an exterior surface and in an at least one pore of a 13X molecular sieve. No reducing catalyst component is utilized to form Comparative Example 1.

More specifically, 0.2 g of bis(cyclopentadienyl)zirconium(IV) (Zr) is combined with 100 ml of toluene and 150 ml of methyl ethyl ketone to form a mixture. The mixture and a 13X molecular sieve are combined, air dried for 12 hours, and then dried for 24 hours at 110° C. to dispose Zr, as the depolymerization catalyst component on the exterior surface and in the at least one pore.

Decomposition of Plastics

After each of the catalysts of Example 1, Example 2, and Comparative Example 1 are formed, each is used to independently decompose a mixture of polyethylene and polypropylene (Recycling Codes 4 and 5). More specifically, the plastics for each example are cut into pieces and loaded into a heated vessel in the presence of the aforementioned catalysts. The plastics are exposed to a constant stream of nitrogen (N₂) and hydrogen (H₂) and heated to 450° C. At approximately 380° C., products from the decomposition of the plastics start to distill over.

At the end of the trial, the hydrocarbons are analyzed via GC/MS (gas chromatography/mass spectroscopy) to determine highest yield of the hydrocarbons recovered, highest yield and percent yield of the hydrocarbons recovered for hydrocarbons having 11-25 carbon atoms, and highest yield and percent yield of the hydrocarbons recovered for hydrocarbons having 5-10 carbon atoms. These yields are set forth in Table 1 below. The results of the GC analysis of Example 1, Example 2, and Comparative Example 1 are set forth in FIGS. 5, 6, and 7, respectively.

As shown in Table 1, Inventive Example 1 with the Zr disposed on the external surface and the Pd disposed in the at least one pore generally provides for a higher molecular distribution than Comparative Example 1 with the Zr disposed on the external surface and in the at least one pore. Inventive Example 2 with the Zr disposed on the external surface and in the at least one pore, and the Pd disposed in the at least one pore, generally provides for a higher molecular distribution than both Comparative Example 1 and Inventive Example 1. More specifically, Inventive Examples 1 and 2 provides a higher yield of hydrocarbons having 11 to 25 carbon atoms than Comparative Example 1 and Inventive Example 2 provides a higher yield of hydrocarbons having 11 to 25 carbon atoms than Inventive Example 1. As described previously, diesel fuel typically includes hydrocarbons having 11 to 25 carbon atoms. Without intending to be bound by any particular theory, it is believed that the Zr and the Pd in the at least one pore of Inventive Example 2 cooperate synergistically thereby increasing yield of hydrocarbons having 11 to 25 carbon atoms during decomposition of the plastic.

TABLE 1 Comparative Example 1 Example 2 Example 1 Porous Support 13X Molecular Sieve 13X Molecular Sieve 13X Molecular Sieve Catalyst in Pore Pd Pd and Zr Zr Catalyst on Zr Zr Zr Surface Reducing Agent H₂ H₂ H₂ High C9, C12, C12, C14, C5, C6, C9, C12, C14 Hydrocarbons C14, C16, C18, C20, C22 C16, C18, C20, C22, C24 Highest C8-C9 C9 C5-C9 Hydrocarbons (C₅-C₁₀) Highest C12-C24 C12-C12 C11-C18 Hydrocarbons (C₁₁-C₂₅) Percent Gasoline 52 5 59 (C₅-C₁₀) Percent Diesel 48 95 41 (C₁₁-C₂₅)

Additional Examples Inventive and Comparative

Additional examples of the catalyst are formed. The technique used to generate the data relative to these additional examples is EDS (Energy Dispersive X-Ray Spectroscopy). This technique detects elements on the surface of a material, i.e., usually on the top layer of the material. The characterization capabilities of EDS are due in large part to the fundamental principle that each element has a unique atomic structure which allows a unique set of electromagnetic emission peaks to be emitted and shown in a spectrum. When a high energy X-ray hits the surface of the material, different elements on the surface of the material emit unique peaks that are detected. The area under the peaks can be used to calculate an approximate concentration of the elements on the surface of the material.

This technique can be easily and readily used to determine physical properties of the porous support such as presence of particular elements both on the exterior surface of the porous support and within the pores of the porous support. Moreover, the accuracy and precision of EDS is high and the number of EDS tests that need to be completed to determine various physical properties is low.

Relative to these additional examples, the porous support used is an aluminum silicate with pore channels of similar diameters running the entire length of the porous support. More specifically, the pores of the porous support have an average pore size of 10 Angstroms (i.e., the porous support is categorized as 13X). Any porous material, including glass or ceramic, could also be used and the same results would be expected.

The porous support is exposed to a catalyst solution that includes a catalyst and a solvent that is compatible with the catalyst. Catalyst “compatibility” s typically based on solubility. For example, the nickel reducing catalyst used herein is compatible with water but not with toluene because of solubility.

The porous support is exposed to a volume of the catalyst solution that is required to fill all the pores such that the catalyst solution is drawn into the pores by capillary action. This volume is provided by the manufacturer of the porous support. The catalyst is then precipitated by a chemical action, thermal action, or a combination of chemical and thermal actions, inside the pores. This deposits the catalyst inside of the pores but not on the exterior surface of the porous support.

After filling the pores with one solvent, a second catalyst solution is used. The second catalyst solution includes a second catalyst and a solvent that is not compatible with the first solvent (now occupying the pores of the porous support). This lack of compatibility is based on polarity or solubility. The second catalyst is precipitated primarily on the exterior surface of the porous support when the non-compatible solvent is removed.

If the pores of the porous support are first filled with a nickel catalyst dissolved in water, then the nickel catalyst will be deposited inside of the pores but not on the exterior surface of the porous support when the water is removed. Before removing the water in the pores or filling up again with water, if a zirconium catalyst is then dissolved in toluene, and the porous support is exposed to the solution of the zirconium catalyst and the toluene, the zirconium catalyst will be precipitated only on the outer surface of the porous support when toluene is removed because water and toluene are not compatible. Therefore, it is clear that the zirconium catalyst will not be substantially deposited in any of the pores and will remain mostly on the exterior surface of the porous support while the nickel catalyst will be deposited within the pores of the porous support and not substantially on the exterior surface of the porous support. These methods are used in these additional examples.

Choice of the catalysts and the solvents allows for: (1) preferential disposition of one catalyst (such as a depolymerization catalyst) on the exterior surface of the porous support with minimal deposition inside the pores, and (2) preferential disposition of another catalyst (such as a reducing catalyst) inside of the pores of the porous support with minimal deposition on the exterior surface of the porous support. In the alternative, incompatibility of solvents can be used to deposit one catalyst in the pores of the porous support or on the external surface of the porous support and then to deposit another catalyst both inside the pores of the porous support and on the exterior surface of the porous support.

Examples of catalysts are set forth below wherein a zirconium depolymerization catalyst is deposited on the exterior surface of the porous support for both Catalysts A and B.

Relative specifically to Catalyst A, a nickel reducing catalyst is deposited both on the exterior surface of the porous support and within the pores of the porous support. Therefore, Catalyst A is a comparative example.

Relative specifically to Catalyst B, no zirconium depolymerization catalyst is purposely disposed within the pores of the porous support. Moreover, the nickel reducing catalyst is preferentially deposited inside the pores of the porous support. However, the exterior surface of the porous support comprises less than 10 parts by weight of the nickel reducing catalyst based on 100 parts by weight of the zirconium depolymerization catalyst component as determined using Energy Dispersive X-Ray Spectroscopy (EDS). Therefore, Catalyst B is an inventive example.

More specifically, Catalysts A and B are formed as follows:

Catalyst A:

29.25 g of nickel nitrate (Ni(NO₃)₄.6H2O is dissolved in 240 ml of water. This solution is mixed with 500 grams of 13X zeolite (as a porous support), whose pore volume is reported by the manufacturer to be 140 ml. After stirring well, the mixture is maintained at 110° C. overnight and then heated to 300° C. to deposit finely divided nickel as the reducing catalyst inside the pores of the porous support and on the exterior surface of the porous support.

Subsequently, about 1 g of bis(cyclopentadienyl) zirconium (IV), as a depolymerization catalyst, is dissolved in 200 g of Toluene and 40 g of methyl ethyl ketone. This mixture is then added to 100 g of the zeolite/nickel catalyst above at room temperature and stirred. The solvents are then removed at 110° C. overnight. This removal of the solvents precipitates the bis(cyclopentadienyl) zirconium depolymerization catalyst inside the pores of the porous support and on the exterior surface of the porous support.

Catalyst B:

29.25 g of nickel nitrate (Ni(NO₃)₄.6H2O) is dissolved in 240 ml of water. 100 ml of the solution is mixed with 500 grams of 13X zeolite, whose pore volume is reported by the manufacturer to be 140 ml. After stirring well, the mixture is maintained at 110° C. overnight and then heated at 300° C. to deposit finely divided nickel reducing catalyst inside the pores of the porous support but not substantially on the exterior surface of the porous support.

Subsequently, 140 ml of water is added to the 500 g of zeolite with the nickel reducing catalyst deposited in the pores of the porous support as prepared above. After stirring well, about 1 g of bis(cyclopentadienyl) zirconium (IV), as a depolymerization catalyst, is dissolved in 200 g of Toluene and is added to 100 g of the aforementioned catalyst at room temperature and stirred. The solvents are then removed by evaporation at 110° C. overnight. This removal of the solvents precipitates the bis(cyclopentadienyl) zirconium (IV) depolymerization catalyst on the outer surface of the porous support such that no zirconium is detected within the pores. Moreover, the nickel reducing catalyst is deposited in the pores of the porous support such that the exterior surface comprises less than 10 parts by weight of the reducing catalyst component based on 100 parts by weight of the depolymerization catalyst component as determined using Energy Dispersive X-Ray Spectroscopy (EDS).

After formation, samples of Catalysts A and B are analyzed using Energy Dispersive X-Ray spectroscopy (EDS) for semi-quantitative identification of elements with atomic numbers greater than 5. The EDS is used to determine the amount of the nickel catalyst on the exterior surface of the porous support and amount of the nickel catalyst inside the pores of the porous support for both Catalysts A and B. The resulting approximate EDS spectra are set forth in FIGS. 8A-9B and the identified elements and semi-quantitative interpretation are annotated below each spectrum.

The data set forth in the Figures relative to Catalyst A clearly shows that the nickel catalyst is present in approximately the same relative amount both on the exterior of the porous support of the catalyst and also within the pores of the porous support.

The data set forth in the Figures relative to Catalyst B clearly shows that the nickel of the nickel catalyst is present in a much higher relative amount within the pores of the porous support than on the exterior surface of the porous support. In other words, the exterior surface of Catalyst B comprises less than 10 parts by weight of the nickel reducing catalyst based on 100 parts by weight of the depolymerization catalyst component as determined using Energy Dispersive X-Ray Spectroscopy (EDS).

The EDS spectra also indicate the presence of zirconium on the exterior surfaces and within the pores (not quantified). The zirconium originates from the bis(cyclopentadienyl) zirconium (IV) depolymerization catalyst that is used in both Catalysts A and B. In Catalyst B, the zirconium is deposited only on the outer surfaces of the porous support. The EDS spectra confirms the absence of zirconium inside the pores of the porous support of Catalyst B. The EDS spectra also show that the nickel reducing catalyst is:

Deposited on the exterior surface of the porous support and within the pores of Catalyst A, and

Deposited in the pores of the porous support of Catalyst B such that the exterior surface of the porous support of Catalyst B comprises less than 10 parts by weight of the nickel reducing catalyst based on 100 parts by weight of the depolymerization catalyst component as determined using Energy Dispersive X-Ray Spectroscopy (EDS).

The data also shows that the amount of nickel reducing catalyst deposited on the exterior surface of the porous support in Catalyst B is less than 10 parts by weight based on 100 parts by weight of the bis(cyclopentadienyl) zirconium (IV) depolymerization catalyst. This is calculated as follows and is based on the fact that area percents of the different elements can be used to represent the proportions of these elements in weight.

The EDS spectra show that the zirconium depolymerization catalyst is deposited within the pores of Catalyst A and on the surface of the porous support of Catalyst A. However, the EDS spectra show no zirconium depolymerization catalyst is deposited in the pores of the porous support of Catalyst B.

More specifically, 29.25 grams of nickel nitrate is used to form the nickel reducing catalyst in each of Catalysts A and B. This is equivalent to 5.9 grams of elemental nickel. 1 gram of bis(cyclopentadienyl) zirconium (IV) is also used to form each of the Catalysts A and B. Unlike the nickel reducing catalyst wherein elemental nickel is the actual reducing catalyst, the zirconium depolymerization catalyst is not elemental zirconium but instead is the bis(cyclopentadienyl) zirconium(IV) molecule. Therefore, the amount of the zirconium depolymerization catalyst used is 1 gram.

Relative to Catalyst A, the EDS spectra show that approximately 50% wt of the nickel is deposited within the pores of the porous support and approximately 50% wt of the nickel is deposited on the exterior surface of the porous support. That is, approximately 2.95 g of nickel are deposited within the pores and 2.95 g of nickel are deposited on the exterior surface of the porous support in 500 g of Catalyst A. Moreover, the EDS spectra show that the 1 g of zirconium catalyst is deposited on the exterior surface of 100 g of the porous support and within the pores of the porous support on Catalyst A. Therefore, the nickel reducing catalyst is present on the exterior surface of the porous support in an amount of about 0.59 g per 0.5 g of the zirconium depolymerization catalyst.

Relative to Catalyst B, the EDS spectra show that all of the zirconium catalyst is deposited on the exterior surface of the porous support and no zirconium catalyst is deposited within the pores of the porous support. Therefore, all the 1 g of zirconium catalyst is deposited on the exterior surface of the porous support of Catalyst B.

The values listed under the EDS spectrum are the area percent values. To compare the values from two different spectra, the values have to be ‘normalized’. The area percent of oxygen is used and the area percent values of nickel are normalized to the area percent of oxygen as 50%. The normalized value of nickel is 0.345% on the exterior surface of the porous support and 4.95% in the pores of the porous support in Catalyst B. Since only 100 g of the zeolite (out of 500 g initially used) with nickel precipated in the pores only is used to deposit the zirconium catalyst on the surface, this calculates to 0.069 g of nickel on the exterior surface of the porous support and 1 g of nickel in the pores of the porous support of Catalyst B (less than 10% on the outer surface).

The calculated amounts of nickel (based on area percent) present are 0.069 g on the exterior surface of the porous support of Catalyst B. Therefore, (0.069 g nickel catalyst/1 g zirconium catalyst)×100=6.9 wt % or 6.9 parts by weight of the nickel catalyst per 100 parts by weight of the zirconium catalyst, which is less than the 10 parts by weight of the claims. As a result, it is clear to me as one of skill in the art that the exterior surface of the porous support comprises less than 10 parts by weight of the nickel reducing catalyst based on 100 parts by weight of the zirconium depolymerization catalyst as determined using Energy Dispersive X-Ray Spectroscopy (EDS).

The data and testing set forth above and in the Figures clearly and unequivocally demonstrate that the catalyst of the instant invention can be formed and successfully tested using EDS to determine the location of the catalysts relative to the porous support and approximate amounts of the catalysts.

Evaluation of Catalysts A and B:

After formation, Catalysts A and B are used to de-polymerize plastics to diesel-like fuel according to the following procedure:

High density polypropylene is cut into pieces and loaded into a heated vessel. In a first heated vessel, 1000 grams of molten high density polypropylene is combined with 10 grams of Catalyst A. In a second heated vessel, 1000 grams of the molten high density polypropylene is combined with 10 grams of Catalyst B.

The high density polypropylene in both heated vessels is exposed to a constant stream of nitrogen (N2)+hydrogen (H2) and heated to 400° C. At approximately 400° C., the depolymerized mixture of hydrocarbons is collected from each of the heated vessels and sent to Paragon Laboratory, in Livonia, Mich. to determine the physical characteristics of the products recovered. These physical characteristics are then compared to specified ASTM specification of diesel-like fuel. The results are set forth immediately below:

ASTM Diesel Physical Property Catalyst A Catalyst B Specifications Derived Cetane no. 31.9 64 >40 (ASTM D976) Viscosity @ 4° C. 1.019 mm²/sec 2.929 mm²/sec 1.9-4.1 mm²/sec ASTM 445 Density @ 15° C. 0.773 g/cm³ 0.7982 g/cm³ 0.85 g/cm³ ASTM 4052 API density @ 15° C. 51.5 45.6 ~40 ASTM 4052 Flash point <70° F. <70° F. >100° F.

This data clearly shows that the fuel products obtained using Catalyst B are superior to the fuel products obtained using Catalyst A. For example, the data shows that the derived cetane numbers of the fuel products generated using Catalyst B are actually better than from pump bought diesel and better than the numbers of the fuel products generated using Catalyst A (wherein higher/greater numbers are better).

The data also shows that viscosity and density of the fuel products that are obtained using Catalyst B are clearly more consistent with ASTM diesel specifications as compared to the viscosity and density of the fuel products obtained using Catalyst A.

The data further shows that flash points of both the fuel products that are obtained using Catalysts A and B are lower than ASTM diesel specifications mainly due to the presence of about 5% of gasoline in the products (per GC/MS). Better results with Catalyst B may be due to the reducing catalyst in the pores of the porous support being better able to hydrogenate double bonds, stopping any further depolymerization. If the reducing catalyst is present on the exterior surface of the porous support, the reducing capacity is diminished. Also, relative to the fuel products obtained using Catalyst A, the depolymerization catalyst is present inside the pores of the porous support such that the depolymerization reaction is competing with the reduction/hydrogenation reaction, thus providing a product that greatly differs from ASTM diesel specifications.

It is contemplated that, in one or more non-limiting embodiments, one or more compounds, chemistries, method steps, components, etc., as described in the PCT Application PCT/US2012/071291, U.S. patent application Ser. No. 14/366,851, or any provisional patent application to which the PCT application and/or the US patent application claims priority, the entireties of which are expressly incorporated herein by reference, may be utilized.

One or more of the values described above may vary by ±5%, ±10%, ±15%, ±20%, ±25%, etc. so long as the variance remains within the scope of the disclosure. Unexpected results may be obtained from each member of a Markush group independent from all other members. Each member may be relied upon individually and or in combination and provides adequate support for specific embodiments within the scope of the appended claims. The subject matter of all combinations of independent and dependent claims, both singly and multiply dependent, is herein expressly contemplated. The disclosure is illustrative including words of description rather than of limitation. Many modifications and variations of the present disclosure are possible in light of the above teachings, and the disclosure may be practiced otherwise than as specifically described herein. 

1-24. (canceled)
 25. A catalyst for recycling a plastic chosen from polyethylene, polypropylene, polystyrene, and combinations thereof, said catalyst comprising: a porous support having an exterior surface and at least one pore therein; a depolymerization catalyst component comprising a metallocene catalyst disposed on said exterior surface of said porous support; and a reducing catalyst component disposed in said at least one pore; wherein said exterior surface of said porous support comprises less than 10 parts by weight of said reducing catalyst component based on 100 parts by weight of said depolymerization catalyst component as determined using Energy Dispersive X-Ray Spectroscopy (EDS), wherein said reducing catalyst component comprises a transition metal selected from the group of iron, nickel, palladium, platinum, and combinations thereof, and wherein said at least one pore in the porous support has an average pore size of 10 Angstroms.
 26. The catalyst of claim 25 wherein said metallocene catalyst comprises zirconium.
 27. The catalyst of claim 26 wherein said metallocene catalyst is bis(cyclopentadienyl)zirconium(IV).
 28. The catalyst of claim 25 wherein said porous support is a molecular sieve.
 29. The catalyst of claim 25 wherein said porous support is a 13X molecular sieve.
 30. The catalyst of claim 25 wherein the plastic is decomposed to form a hydrocarbon having 4 to 40 carbons.
 31. The catalyst of claim 25 wherein the plastic is decomposed to form a hydrocarbon having 5 to 25 carbons.
 33. The catalyst of claim 31 wherein the hydrocarbon having 5 to 25 carbons is gasoline, diesel fuel, or a combination thereof.
 34. The catalyst of claim 25 wherein the polyethylene is selected from the group of low density polyethylene, linear low density polyethylene, high density polyethylene, and combinations thereof.
 35. The catalyst of claim 25 wherein the plastic consists essentially of polyethylene, polypropylene, and combinations thereof.
 36. The catalyst of claim 35 wherein the polyethylene is selected from the group of low density polyethylene, linear low density polyethylene, high density polyethylene, and combinations thereof.
 37. The catalyst of claim 25 wherein said reducing catalyst component comprises nickel.
 38. The catalyst of claim 25 wherein said reducing catalyst component comprises iron.
 39. The catalyst of claim 25 wherein said exterior surface of said porous support comprises less than 5 parts by weight of said reducing catalyst component based on 100 parts by weight of said depolymerization catalyst component as determined using Energy Dispersive X-Ray Spectroscopy (EDS).
 40. A catalyst for recycling a plastic to form diesel fuel, wherein the plastic is chosen from polyethylene, polypropylene, polystyrene, and combinations thereof and wherein said catalyst consists essentially of: a porous support having an exterior surface and at least one pore therein; a depolymerization catalyst component that is bis(cyclopentadienyl)zirconium(IV) and is disposed on said exterior surface of said porous support; and a reducing catalyst component disposed in said at least one pore; wherein said exterior surface of said porous support comprises less than 10 parts by weight of said reducing catalyst component based on 100 parts by weight of said depolymerization catalyst component as determined using Energy Dispersive X-Ray Spectroscopy (EDS), wherein said reducing catalyst component comprises a transition metal selected from the group of iron, nickel, palladium, platinum, and combinations thereof, and wherein said at least one pore in the porous support has an average pore size of 10 Angstroms.
 41. The catalyst of claim 40 that consists of said porous support, said depolymerization catalyst, and said reducing catalyst.
 42. The catalyst of claim 40 wherein said exterior surface of said porous support comprises less than 5 parts by weight of said reducing catalyst component based on 100 parts by weight of said depolymerization catalyst component as determined using Energy Dispersive X-Ray Spectroscopy (EDS).
 43. A catalyst for recycling a plastic to form diesel fuel having 5 to 25 carbons, wherein the plastic is chosen from polyethylene, polypropylene, polystyrene, and combinations thereof and wherein said catalyst consists essentially of: a porous support having an exterior surface and at least one pore therein; a depolymerization catalyst component that is bis(cyclopentadienyl)zirconium(IV) and is disposed on said exterior surface of said porous support; and a reducing catalyst component that is nickel nitrate and that is disposed in said at least one pore; wherein said exterior surface of said porous support comprises less than 5 parts by weight of said reducing catalyst component based on 100 parts by weight of said depolymerization catalyst component as determined using Energy Dispersive X-Ray Spectroscopy (EDS), and wherein said at least one pore in the porous support has an average pore size of 10 Angstroms and is a 13X molecular sieve. 